With a rapid development of information technology, portable electronic devices, such as mobile phones and tablet PCs have various functions that bring great convenience to people's daily life. Portable electronic devices are convenient to carry. Portable electronic devices, such as mobile phones, are also used to store information. However, most portable electronic devices can only be used as slave devices. That is, they connect to master devices such as computers through data lines to achieve data exchanging between storing devices. The common electronic devices cannot extend their memory through direct connection to external storing devices, which is not convenient for people to use these electronic devices. Besides, with diversification of functions of the electronic devices, people use electronic devices more and more frequently. As a result, ordinary electronic devices run out of power easily, causing inconvenience in people's daily life.